The process of nickel electroplating on iron substrate mainly includes three key stages: pre-treatment, electroplating and post-treatment.
Author: Marisa
The process of nickel electroplating on iron substrate mainly includes three key stages: pre-treatment, electroplating and post-treatment.
1. Pretreatment (surface preparation)
Pretreatment is the key to electroplating quality, ensuring that the substrate surface is clean and free of impurities such as oil, oxides, etc.
1)Mechanical treatment
Grinding/polishing: Use sandpaper or polishing machine to remove surface burrs and rust to improve the finish of the substrate.
Sandblasting (optional): For rough surfaces, enhance the adhesion of the coating.
2)Degreasing
Chemical degreasing: Soak in alkaline solution (such as NaOH, Na₂CO₃, Na₃PO₄, etc., temperature 50-80℃) for 5-10 minutes to remove oil stains.
Electrolytic degreasing (optional): Further cleaning by cathode or anodic electrolysis (current density 3-10 A/dm²).
3)Pickling (activation)
Soak in dilute hydrochloric acid (10-20%) or sulfuric acid (5-10%) for 30 seconds to 2 minutes to remove the oxide film and expose the fresh iron surface.
Note: Avoid excessive corrosion and rinse thoroughly after pickling.
4)Washing
Rinse with running water after each step to prevent contamination of subsequent bath liquid.
2. Nickel electroplating
Plated solution composition (taking Watt nickel as an example):
1)Nickel sulfate (NiSO₄·6H₂O): 200-300 g/L
2)Nickel chloride (NiCl₂·6H₂O): 30-60 g/L (provides chloride ions to promote anode dissolution)
3)Boric acid (H₃BO₃): 30-40 g/L (pH buffer)
4)Additives: wetting agent (such as sodium dodecyl sulfate), brightener (added as needed).
Process parameters:
1)pH value: 3.5-4.5 (adjusted with dilute sulfuric acid or NaOH)
2)Temperature: 45-60℃
3)Current density: 1-10 A/dm² (adjusted according to coating thickness)
4）Time: 10-60 minutes (coating thickness is usually 5-20μm).
Steps:
1）Immerse the iron part in the nickel plating tank and connect the power supply as the cathode.
2）Use a nickel plate (or nickel ball) as the anode.
3）After power is turned on, nickel ions are reduced and deposited on the surface of the cathode (iron part) to form a coating.
3. Post-treatment
1）Water washing: Immediately wash with deionized water after electroplating to prevent salt residue.
2）Passivation (optional): Chromate passivation (such as CrO₃ solution) improves corrosion resistance.
3）Neutralization: Weak alkaline solution (such as Na₂CO₃) neutralizes residual acid.
4）Drying: Hot air drying or centrifugal dehydration to avoid water stains.
5）Inspection: Check the appearance of the coating (no blistering, peeling), thickness (thickness gauge), and corrosion resistance (salt spray test).
Precautions
1）Plating solution maintenance: Regularly filter, analyze, add main salt and additives to prevent impurities from accumulating.
2）Anti-hydrogen embrittlement: For high-strength steel, it is necessary to bake at 200℃ for 2-4 hours to remove hydrogen.
3）Environmental protection: Waste liquid needs to be neutralized (such as nickel ion precipitation recovery) to meet emission standards.
Through the above process, a nickel plating layer with strong bonding, uniformity and density can be obtained on the iron substrate, which can be used for corrosion protection, decoration or subsequent plating of other metals (such as chromium and gold).